Like its close cousins garlic, chives, scallions, and leeks, onion is
a member of the lily family (Liliaceae). It is native to Eurasia but
now grows all over the world, due mostly to people bringing it with them
as a staple food wherever they migrated. The French explorer Pere
Marquette was saved from starvation in 1624 by eating wild onions near
the present site of Chicago—the name of the city is derived from a
Native American word for the odor of onions. The bulb of the plant is
used medicinally.

Uses

Type 1 and Type 2 Diabetes20 grams fresh onion three times per day
Large amounts of onion have been shown to lower blood sugar levels in
people with diabetes, possibly by blocking the breakdown of insulin in
the liver.

Traditional Use (May Not Be Supported by
Scientific Studies)
Onion has been used as food for many centuries. Onion was also a popular
folk remedy, being applied to tumors, made into a syrup for relieving
coughs, or prepared in a tincture (using gin) to relieve “dropsy” (heart
failure–related edema). It was considered a weaker version of garlic by
many herbal practitioners. Like garlic, onion has a longstanding but
unsubstantiated reputation as an aphrodisiac.

How to Use It
Most human studies that have shown an effect from onions used at least
25 grams per day and often two to four times that amount. Though some
studies have found cooked onions acceptable, several studies suggest
that onion constituents are degraded by cooking and that fresh or raw
onions are probably most active.

Side Effects
Most people can eat onion in food without any difficulties. Higher
intakes of onion may worsen existing heartburn, though it does not seem
to cause heartburn in people who do not already have it. There are also
isolated reports of allergy to onion, including among people with
asthma, manifesting as skin rash and red, itchy eyes.

Onion is safe for use in children and, in small amounts in food,
during pregnancy (though some pregnant women may have heartburn that
onions could exacerbate) and nursing. It is unknown whether larger
amounts of onion are safe during pregnancy and nursing. One study did
find that baby rats nursing from mothers that were fed onion developed a
taste for onion and suffered no ill effects.

Interactions with Supplements, Foods,
& Other Compounds
At the time of writing, there were no well-known interactions with this
supplement.